Proper nervous system function requires that neural tissue be precisely patterned so that different kinds of neurons and glia develop at correct times and places and axons reach their appropriate targets. In vertebrate embryos, floorplate has a critical role in patterning, as it is the source of molecules that influence neural cell fate and guide axons. Thus, understanding how floorplate cells are specified is fundamental to understanding neural development and function. The research proposed uses genetic analysis to test the role of Delta-Notch mediated cell interactions and learn how multiple gene functions are integrated as a means to elucidate the mechanisms that specify cell fates in the vertebrate midline. Specifically, this application first proposes to learn how fates of individual precursor cells correlate with their positions in the midline, as well as how neighboring precursor cells interact during gastrulation. Experiments are then proposed to learn how expression of genes important to midline development corresponds with the distribution of precursor cells in the midline. Next, it addresses the role of Delta-Notch mediated cell interactions in patterning the midline through observation of cell behaviors in mutant embryos and disruption of Delta-Notch interactions specifically at the midline. Finally, it proposes to combine mutant analysis and gene overexpression experiments to investigate how multiple signaling pathways are integrated to pattern the midline and specify floorplate.